Write Buffer Command (3Bh) - Seagate SCSI Interface Product Manual

SCSI Interface Product Manual, Rev. J
5.51

Write Buffer command (3Bh)

The Write Buffer command may be used in conjunction with the Read Buffer command as a diagnostic function
for testing the drive's data buffer memory and the SCSI bus integrity. When used in a diagnostic mode, the
medium shall not be accessed during the execution of this command. Additional modes are provided for down-
loading and saving executable microcode.
The function of this command and the meaning of the fields within the Command Descriptor Block depend on
the mode field (Byte 1, data bits 0, 1, 2). See note [2] of Table 173.
Table 173: Write Buffer command (3Bh)
Bit 7
Byte
0 0
1 0
Logical Unit Number [1]
2 Buffer ID [5]
3 (MSB)
4
5
6 (MSB)
7
8
9 0
Notes.
[1] The Logical Unit Number must be zero.
[2] The Mode field is defined in the following table and in the referenced sections.
Check with individual drive's Product Manual, Volume 1, to see which modes are supported by the drive in
question.
DB3 DB2 DB1
0 0 0
0 0 0
0 0 1
0 1 0
0 1 0
0 1 1
0 1 1
1 0 1
1 0 0
1 0 0
1 0 1
: : :
1 1 1
[3] Use a Read Data Buffer command with mode bits set to 0011b to get the drive buffer capacity to use with
the Write Buffer command.
[4] See "Control byte," paragraph 4.2.6. All bits are zero for all modes.
[5] Implemented only by drives that support modes 0110b and 0111b.
6 5
0 1
0 0
Reserved
Byte Transfer Length [3]
0 0
DB0 Mode definition
0 Write combined header and data (Section 5.51.1)
1 Reserved
0 Write data (Section 5.51.2)
0 Download microcode (Section 5.51.3)
1 Download microcode and save (Section 5.51.4)
0 Download microcode with offsets (Section 5.51.5)
1 Download microcode with offsets and save (Section 5.51.6)
0 Write data to echo buffer (Section 5.51.7)
0 Reserved
1 Reserved
1 Reserved
: Reserved
1 Reserved
4 3
1 1
0
Buffer Offset [5]
0 0
2 1
0 1
Mode [2]
(LSB)
(LSB)
0 Flag [4] Link [4]
215
0
1